1. Field of the Invention
The present invention relates to an apparatus and a method for checking leakage of fluid, such as air, fuel vapor, liquid fuel, etc., from a fuel vapor processing apparatus that includes a canister communicating with a fuel tank of an automobile via a communication passage.
2. Description of the Related Art
A known method for checking leakage of fluid from a fuel vapor processing apparatus is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2004-270573. As shown in FIG. 6, a fuel vapor processing apparatus 100 disclosed in this publication includes a vapor passage 104 for introducing fuel vapor produced within a fuel tank T into a canister 102, an atmospheric-side opening and closing device 105 having a throttle and provided at the canister 102, and a recovery passage 103 communicating between the canister 102 and an intake air passage 107 of an engine. A jet pump 106 is disposed within the fuel tank T for generating a negative pressure. The jet pump 106 communicates with the intake air passage 107 of the engine via an intake air pipe 108.
In order to check leakage from the fuel vapor processing apparatus 100, a valve 103v provided in the recovery passage 103 is closed and the jet pump 106 is operated on the condition that the atmospheric-side opening and closing device 105 is operated to open through the throttle. Then, an external air is introduced into the fuel tank T via the intake air passage 107 and the intake air pipe 108 of the engine, so that the pressure within the fuel tank T as well as the pressure within the canister 102 communicating with the fuel tank T via the vapor passage 104 increases. The pressure increase curve measured at that time is compared with a reference pressure increase curve for checking leakage.
According to the method for checking leakage disclosed in the above publication, the internal space of the fuel tank T and the internal space of the canister 102 are pressurized for checking leakage. Therefore, it is necessary to introduce a large amount of external air into the fuel tank T and the canister 102. This also requires that a large amount of air is discharged to the outside after checking leakage. When a large amount of air is discharged to the outside, it may be possible that fuel vapor adsorbed and retained within the canister 102 is discharged to the outside together with the air.
Therefore, there is a need in the art for an apparatus and a method for checking leakage of fluid from a fuel vapor processing apparatus, which doe not require introduction of a large amount of air for checking.